Effective Absorption Mechanism of SO 2 and NO 2 in the Flue Gas by Ammonium-Bromide-Based Deep Eutectic Solvents.

Simultaneous capture of SO 2 and NO x from flue gas is critical for coal-fired power generation. In this study, environmentally friendly and high-performance deep eutectic solvents based on ethylene glycol and ammonium bromide were designed to capture SO 2 and NO 2 simultaneously. The SO 2 and NO 2 absorption performances and absorption mechanisms were systematically investigated by 1 H NMR and Fourier transform infrared (FT-IR) spectroscopy in combination with ab initio calculations using Gaussian software. The results showed that EG-TBAB DESs can absorb low concentrations of SO 2 and NO 2 from the flue gas simultaneously at low temperatures (≤50 °C). 1 H NMR, FT-IR, and simulation results indicate that SO 2 and NO 2 are absorbed by forming EG-TBAB-SO 2 -NO 2 complexes, Br - is the main active site for NO 2 absorption, and NO 2 is more active in an EG-TBAB-NO 2 -SO 2 complex than SO 2 . EG-TBAB DESs exhibit outstanding regeneration capability, and absorption capacities remain unchanged after five absorption-desorption cycles. The fundamental understanding of simultaneous capture of SO 2 and NO 2 from this study enables DES structures to be rationally designed for efficient and low-cost desulfurization and denitrification reagents.